LPL's other original private-equity investor, TPG Capital LP, will also distribute a portion of its holdings of LPL stock to its partners. After that distribution, TPG will have about a 17% stake remaining in the company.

The total distribution of $16.6 million shares was expected to happen today. The distribution represents about 16% of the company's total shares outstanding.

Limited partners in such private-equity funds can either hold on to or sell the stock in such distributions. The two firms previously distributed 12.5 million shares to their respective partners in May 2013.

Although the private equity firms acted on their own this month, news of the ownership shift sparked speculation that LPL could be interested in forming its own bank to sweep client cash. Banking regulations do not allow companies with private-equity ownership of more than 25% to have banks.

LPL chief executive Mark Casady mentioned the possibility of a company-owned bank last month on an earnings call with analysts.

Most major brokerage firms sweep client cash into insured bank accounts, using the funds as a source of low-cost deposits.

Ms. Weinberger said the company has no immediate plans to form its own bank.

But “we noticed that CEO Mark Casady had all the arguments for a bank at his fingertips on the recent earnings call,” said Sanford C. Bernstein & Co. LLC analysts Brad Hintz and Luke Montgomery in a research note Thursday.

If LPL could boost its interest margin from an estimated 62 basis points to the 140 basis points The Charles Schwab Corp. earns on cash sweeps, LPL could more than double the $138 million it earns now on swept cash, the Bernstein analysts said, which would provide about an extra dollar in per-share earnings.

How a bank would impact LPL brokers or their clients is unclear.

Currently, clients get from one to five basis points on their cash deposits, said one representative at the firm who did not want to be identified.

Even if LPL paid a bit more on cash, the amount would be immaterial at this point, the broker said.

LPL stock has been flirting recently with all-time highs as the company has been buying back shares.

On Aug. 9, the stock closed at $39.36 a share, its high. The price of the stock was down more than 3% in trading this morning, trading at $37.34 a share.

The company has repurchased 11.8 million shares since its 2010 initial public offering and has another $198 million set aside for share buybacks, LPL said in a statement.

Hellman & Friedman is also giving up its two seats on LPL's board.

Both Hellman & Friedman and TPG have been investors in LPL since 2005 and together owned 61% of the stock after LPL's IPO.